blob: 54346ed02412d505cce2c95db9afac5d0e22b38f [file] [log] [blame]
// SPDX-License-Identifier: GPL-2.0
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/mmu_notifier.h>
#include <linux/rmap.h>
#include <linux/swap.h>
#include <linux/mm_inline.h>
#include <linux/kthread.h>
#include <linux/khugepaged.h>
#include <linux/freezer.h>
#include <linux/mman.h>
#include <linux/hashtable.h>
#include <linux/userfaultfd_k.h>
#include <linux/page_idle.h>
#include <linux/swapops.h>
#include <linux/shmem_fs.h>
#include <asm/tlb.h>
#include <asm/pgalloc.h>
#include "internal.h"
enum scan_result {
SCAN_FAIL,
SCAN_SUCCEED,
SCAN_PMD_NULL,
SCAN_EXCEED_NONE_PTE,
SCAN_PTE_NON_PRESENT,
SCAN_PAGE_RO,
SCAN_LACK_REFERENCED_PAGE,
SCAN_PAGE_NULL,
SCAN_SCAN_ABORT,
SCAN_PAGE_COUNT,
SCAN_PAGE_LRU,
SCAN_PAGE_LOCK,
SCAN_PAGE_ANON,
SCAN_PAGE_COMPOUND,
SCAN_ANY_PROCESS,
SCAN_VMA_NULL,
SCAN_VMA_CHECK,
SCAN_ADDRESS_RANGE,
SCAN_SWAP_CACHE_PAGE,
SCAN_DEL_PAGE_LRU,
SCAN_ALLOC_HUGE_PAGE_FAIL,
SCAN_CGROUP_CHARGE_FAIL,
SCAN_EXCEED_SWAP_PTE,
SCAN_TRUNCATED,
};
#define CREATE_TRACE_POINTS
#include <trace/events/huge_memory.h>
/* default scan 8*512 pte (or vmas) every 30 second */
static unsigned int khugepaged_pages_to_scan __read_mostly;
static unsigned int khugepaged_pages_collapsed;
static unsigned int khugepaged_full_scans;
static unsigned int khugepaged_scan_sleep_millisecs __read_mostly = 10000;
/* during fragmentation poll the hugepage allocator once every minute */
static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
static unsigned long khugepaged_sleep_expire;
static DEFINE_SPINLOCK(khugepaged_mm_lock);
static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
/*
* default collapse hugepages if there is at least one pte mapped like
* it would have happened if the vma was large enough during page
* fault.
*/
static unsigned int khugepaged_max_ptes_none __read_mostly;
static unsigned int khugepaged_max_ptes_swap __read_mostly;
#define MM_SLOTS_HASH_BITS 10
static __read_mostly DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
static struct kmem_cache *mm_slot_cache __read_mostly;
/**
* struct mm_slot - hash lookup from mm to mm_slot
* @hash: hash collision list
* @mm_node: khugepaged scan list headed in khugepaged_scan.mm_head
* @mm: the mm that this information is valid for
*/
struct mm_slot {
struct hlist_node hash;
struct list_head mm_node;
struct mm_struct *mm;
};
/**
* struct khugepaged_scan - cursor for scanning
* @mm_head: the head of the mm list to scan
* @mm_slot: the current mm_slot we are scanning
* @address: the next address inside that to be scanned
*
* There is only the one khugepaged_scan instance of this cursor structure.
*/
struct khugepaged_scan {
struct list_head mm_head;
struct mm_slot *mm_slot;
unsigned long address;
};
static struct khugepaged_scan khugepaged_scan = {
.mm_head = LIST_HEAD_INIT(khugepaged_scan.mm_head),
};
#ifdef CONFIG_SYSFS
static ssize_t scan_sleep_millisecs_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_scan_sleep_millisecs);
}
static ssize_t scan_sleep_millisecs_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
unsigned long msecs;
int err;
err = kstrtoul(buf, 10, &msecs);
if (err || msecs > UINT_MAX)
return -EINVAL;
khugepaged_scan_sleep_millisecs = msecs;
khugepaged_sleep_expire = 0;
wake_up_interruptible(&khugepaged_wait);
return count;
}
static struct kobj_attribute scan_sleep_millisecs_attr =
__ATTR(scan_sleep_millisecs, 0644, scan_sleep_millisecs_show,
scan_sleep_millisecs_store);
static ssize_t alloc_sleep_millisecs_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_alloc_sleep_millisecs);
}
static ssize_t alloc_sleep_millisecs_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
unsigned long msecs;
int err;
err = kstrtoul(buf, 10, &msecs);
if (err || msecs > UINT_MAX)
return -EINVAL;
khugepaged_alloc_sleep_millisecs = msecs;
khugepaged_sleep_expire = 0;
wake_up_interruptible(&khugepaged_wait);
return count;
}
static struct kobj_attribute alloc_sleep_millisecs_attr =
__ATTR(alloc_sleep_millisecs, 0644, alloc_sleep_millisecs_show,
alloc_sleep_millisecs_store);
static ssize_t pages_to_scan_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_pages_to_scan);
}
static ssize_t pages_to_scan_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long pages;
err = kstrtoul(buf, 10, &pages);
if (err || !pages || pages > UINT_MAX)
return -EINVAL;
khugepaged_pages_to_scan = pages;
return count;
}
static struct kobj_attribute pages_to_scan_attr =
__ATTR(pages_to_scan, 0644, pages_to_scan_show,
pages_to_scan_store);
static ssize_t pages_collapsed_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_pages_collapsed);
}
static struct kobj_attribute pages_collapsed_attr =
__ATTR_RO(pages_collapsed);
static ssize_t full_scans_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_full_scans);
}
static struct kobj_attribute full_scans_attr =
__ATTR_RO(full_scans);
static ssize_t khugepaged_defrag_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return single_hugepage_flag_show(kobj, attr, buf,
TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static ssize_t khugepaged_defrag_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
return single_hugepage_flag_store(kobj, attr, buf, count,
TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);
}
static struct kobj_attribute khugepaged_defrag_attr =
__ATTR(defrag, 0644, khugepaged_defrag_show,
khugepaged_defrag_store);
/*
* max_ptes_none controls if khugepaged should collapse hugepages over
* any unmapped ptes in turn potentially increasing the memory
* footprint of the vmas. When max_ptes_none is 0 khugepaged will not
* reduce the available free memory in the system as it
* runs. Increasing max_ptes_none will instead potentially reduce the
* free memory in the system during the khugepaged scan.
*/
static ssize_t khugepaged_max_ptes_none_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_max_ptes_none);
}
static ssize_t khugepaged_max_ptes_none_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long max_ptes_none;
err = kstrtoul(buf, 10, &max_ptes_none);
if (err || max_ptes_none > HPAGE_PMD_NR-1)
return -EINVAL;
khugepaged_max_ptes_none = max_ptes_none;
return count;
}
static struct kobj_attribute khugepaged_max_ptes_none_attr =
__ATTR(max_ptes_none, 0644, khugepaged_max_ptes_none_show,
khugepaged_max_ptes_none_store);
static ssize_t khugepaged_max_ptes_swap_show(struct kobject *kobj,
struct kobj_attribute *attr,
char *buf)
{
return sprintf(buf, "%u\n", khugepaged_max_ptes_swap);
}
static ssize_t khugepaged_max_ptes_swap_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
int err;
unsigned long max_ptes_swap;
err = kstrtoul(buf, 10, &max_ptes_swap);
if (err || max_ptes_swap > HPAGE_PMD_NR-1)
return -EINVAL;
khugepaged_max_ptes_swap = max_ptes_swap;
return count;
}
static struct kobj_attribute khugepaged_max_ptes_swap_attr =
__ATTR(max_ptes_swap, 0644, khugepaged_max_ptes_swap_show,
khugepaged_max_ptes_swap_store);
static struct attribute *khugepaged_attr[] = {
&khugepaged_defrag_attr.attr,
&khugepaged_max_ptes_none_attr.attr,
&pages_to_scan_attr.attr,
&pages_collapsed_attr.attr,
&full_scans_attr.attr,
&scan_sleep_millisecs_attr.attr,
&alloc_sleep_millisecs_attr.attr,
&khugepaged_max_ptes_swap_attr.attr,
NULL,
};
struct attribute_group khugepaged_attr_group = {
.attrs = khugepaged_attr,
.name = "khugepaged",
};
#endif /* CONFIG_SYSFS */
#define VM_NO_KHUGEPAGED (VM_SPECIAL | VM_HUGETLB)
int hugepage_madvise(struct vm_area_struct *vma,
unsigned long *vm_flags, int advice)
{
switch (advice) {
case MADV_HUGEPAGE:
#ifdef CONFIG_S390
/*
* qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
* can't handle this properly after s390_enable_sie, so we simply
* ignore the madvise to prevent qemu from causing a SIGSEGV.
*/
if (mm_has_pgste(vma->vm_mm))
return 0;
#endif
*vm_flags &= ~VM_NOHUGEPAGE;
*vm_flags |= VM_HUGEPAGE;
/*
* If the vma become good for khugepaged to scan,
* register it here without waiting a page fault that
* may not happen any time soon.
*/
if (!(*vm_flags & VM_NO_KHUGEPAGED) &&
khugepaged_enter_vma_merge(vma, *vm_flags))
return -ENOMEM;
break;
case MADV_NOHUGEPAGE:
*vm_flags &= ~VM_HUGEPAGE;
*vm_flags |= VM_NOHUGEPAGE;
/*
* Setting VM_NOHUGEPAGE will prevent khugepaged from scanning
* this vma even if we leave the mm registered in khugepaged if
* it got registered before VM_NOHUGEPAGE was set.
*/
break;
}
return 0;
}
int __init khugepaged_init(void)
{
mm_slot_cache = kmem_cache_create("khugepaged_mm_slot",
sizeof(struct mm_slot),
__alignof__(struct mm_slot), 0, NULL);
if (!mm_slot_cache)
return -ENOMEM;
khugepaged_pages_to_scan = HPAGE_PMD_NR * 8;
khugepaged_max_ptes_none = HPAGE_PMD_NR - 1;
khugepaged_max_ptes_swap = HPAGE_PMD_NR / 8;
return 0;
}
void __init khugepaged_destroy(void)
{
kmem_cache_destroy(mm_slot_cache);
}
static inline struct mm_slot *alloc_mm_slot(void)
{
if (!mm_slot_cache) /* initialization failed */
return NULL;
return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
}
static inline void free_mm_slot(struct mm_slot *mm_slot)
{
kmem_cache_free(mm_slot_cache, mm_slot);
}
static struct mm_slot *get_mm_slot(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
hash_for_each_possible(mm_slots_hash, mm_slot, hash, (unsigned long)mm)
if (mm == mm_slot->mm)
return mm_slot;
return NULL;
}
static void insert_to_mm_slots_hash(struct mm_struct *mm,
struct mm_slot *mm_slot)
{
mm_slot->mm = mm;
hash_add(mm_slots_hash, &mm_slot->hash, (long)mm);
}
static inline int khugepaged_test_exit(struct mm_struct *mm)
{
return atomic_read(&mm->mm_users) == 0;
}
int __khugepaged_enter(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
int wakeup;
mm_slot = alloc_mm_slot();
if (!mm_slot)
return -ENOMEM;
/* __khugepaged_exit() must not run from under us */
VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
free_mm_slot(mm_slot);
return 0;
}
spin_lock(&khugepaged_mm_lock);
insert_to_mm_slots_hash(mm, mm_slot);
/*
* Insert just behind the scanning cursor, to let the area settle
* down a little.
*/
wakeup = list_empty(&khugepaged_scan.mm_head);
list_add_tail(&mm_slot->mm_node, &khugepaged_scan.mm_head);
spin_unlock(&khugepaged_mm_lock);
mmgrab(mm);
if (wakeup)
wake_up_interruptible(&khugepaged_wait);
return 0;
}
int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
unsigned long vm_flags)
{
unsigned long hstart, hend;
if (!vma->anon_vma)
/*
* Not yet faulted in so we will register later in the
* page fault if needed.
*/
return 0;
if (vma->vm_ops || (vm_flags & VM_NO_KHUGEPAGED))
/* khugepaged not yet working on file or special mappings */
return 0;
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart < hend)
return khugepaged_enter(vma, vm_flags);
return 0;
}
void __khugepaged_exit(struct mm_struct *mm)
{
struct mm_slot *mm_slot;
int free = 0;
spin_lock(&khugepaged_mm_lock);
mm_slot = get_mm_slot(mm);
if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
hash_del(&mm_slot->hash);
list_del(&mm_slot->mm_node);
free = 1;
}
spin_unlock(&khugepaged_mm_lock);
if (free) {
clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
free_mm_slot(mm_slot);
mmdrop(mm);
} else if (mm_slot) {
/*
* This is required to serialize against
* khugepaged_test_exit() (which is guaranteed to run
* under mmap sem read mode). Stop here (after we
* return all pagetables will be destroyed) until
* khugepaged has finished working on the pagetables
* under the mmap_sem.
*/
down_write(&mm->mmap_sem);
up_write(&mm->mmap_sem);
}
}
static void release_pte_page(struct page *page)
{
dec_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page));
unlock_page(page);
putback_lru_page(page);
}
static void release_pte_pages(pte_t *pte, pte_t *_pte)
{
while (--_pte >= pte) {
pte_t pteval = *_pte;
if (!pte_none(pteval) && !is_zero_pfn(pte_pfn(pteval)))
release_pte_page(pte_page(pteval));
}
}
static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
unsigned long address,
pte_t *pte)
{
struct page *page = NULL;
pte_t *_pte;
int none_or_zero = 0, result = 0, referenced = 0;
bool writable = false;
for (_pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, address += PAGE_SIZE) {
pte_t pteval = *_pte;
if (pte_none(pteval) || (pte_present(pteval) &&
is_zero_pfn(pte_pfn(pteval)))) {
if (!userfaultfd_armed(vma) &&
++none_or_zero <= khugepaged_max_ptes_none) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
goto out;
}
}
if (!pte_present(pteval)) {
result = SCAN_PTE_NON_PRESENT;
goto out;
}
page = vm_normal_page(vma, address, pteval);
if (unlikely(!page)) {
result = SCAN_PAGE_NULL;
goto out;
}
VM_BUG_ON_PAGE(PageCompound(page), page);
VM_BUG_ON_PAGE(!PageAnon(page), page);
/*
* We can do it before isolate_lru_page because the
* page can't be freed from under us. NOTE: PG_lock
* is needed to serialize against split_huge_page
* when invoked from the VM.
*/
if (!trylock_page(page)) {
result = SCAN_PAGE_LOCK;
goto out;
}
/*
* cannot use mapcount: can't collapse if there's a gup pin.
* The page must only be referenced by the scanned process
* and page swap cache.
*/
if (page_count(page) != 1 + PageSwapCache(page)) {
unlock_page(page);
result = SCAN_PAGE_COUNT;
goto out;
}
if (pte_write(pteval)) {
writable = true;
} else {
if (PageSwapCache(page) &&
!reuse_swap_page(page, NULL)) {
unlock_page(page);
result = SCAN_SWAP_CACHE_PAGE;
goto out;
}
/*
* Page is not in the swap cache. It can be collapsed
* into a THP.
*/
}
/*
* Isolate the page to avoid collapsing an hugepage
* currently in use by the VM.
*/
if (isolate_lru_page(page)) {
unlock_page(page);
result = SCAN_DEL_PAGE_LRU;
goto out;
}
inc_node_page_state(page,
NR_ISOLATED_ANON + page_is_file_cache(page));
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageLRU(page), page);
/* There should be enough young pte to collapse the page */
if (pte_young(pteval) ||
page_is_young(page) || PageReferenced(page) ||
mmu_notifier_test_young(vma->vm_mm, address))
referenced++;
}
if (likely(writable)) {
if (likely(referenced)) {
result = SCAN_SUCCEED;
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
referenced, writable, result);
return 1;
}
} else {
result = SCAN_PAGE_RO;
}
out:
release_pte_pages(pte, _pte);
trace_mm_collapse_huge_page_isolate(page, none_or_zero,
referenced, writable, result);
return 0;
}
static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
struct vm_area_struct *vma,
unsigned long address,
spinlock_t *ptl)
{
pte_t *_pte;
for (_pte = pte; _pte < pte + HPAGE_PMD_NR;
_pte++, page++, address += PAGE_SIZE) {
pte_t pteval = *_pte;
struct page *src_page;
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
clear_user_highpage(page, address);
add_mm_counter(vma->vm_mm, MM_ANONPAGES, 1);
if (is_zero_pfn(pte_pfn(pteval))) {
/*
* ptl mostly unnecessary.
*/
spin_lock(ptl);
/*
* paravirt calls inside pte_clear here are
* superfluous.
*/
pte_clear(vma->vm_mm, address, _pte);
spin_unlock(ptl);
}
} else {
src_page = pte_page(pteval);
copy_user_highpage(page, src_page, address, vma);
VM_BUG_ON_PAGE(page_mapcount(src_page) != 1, src_page);
release_pte_page(src_page);
/*
* ptl mostly unnecessary, but preempt has to
* be disabled to update the per-cpu stats
* inside page_remove_rmap().
*/
spin_lock(ptl);
/*
* paravirt calls inside pte_clear here are
* superfluous.
*/
pte_clear(vma->vm_mm, address, _pte);
page_remove_rmap(src_page, false);
spin_unlock(ptl);
free_page_and_swap_cache(src_page);
}
}
}
static void khugepaged_alloc_sleep(void)
{
DEFINE_WAIT(wait);
add_wait_queue(&khugepaged_wait, &wait);
freezable_schedule_timeout_interruptible(
msecs_to_jiffies(khugepaged_alloc_sleep_millisecs));
remove_wait_queue(&khugepaged_wait, &wait);
}
static int khugepaged_node_load[MAX_NUMNODES];
static bool khugepaged_scan_abort(int nid)
{
int i;
/*
* If node_reclaim_mode is disabled, then no extra effort is made to
* allocate memory locally.
*/
if (!node_reclaim_mode)
return false;
/* If there is a count for this node already, it must be acceptable */
if (khugepaged_node_load[nid])
return false;
for (i = 0; i < MAX_NUMNODES; i++) {
if (!khugepaged_node_load[i])
continue;
if (node_distance(nid, i) > RECLAIM_DISTANCE)
return true;
}
return false;
}
/* Defrag for khugepaged will enter direct reclaim/compaction if necessary */
static inline gfp_t alloc_hugepage_khugepaged_gfpmask(void)
{
return khugepaged_defrag() ? GFP_TRANSHUGE : GFP_TRANSHUGE_LIGHT;
}
#ifdef CONFIG_NUMA
static int khugepaged_find_target_node(void)
{
static int last_khugepaged_target_node = NUMA_NO_NODE;
int nid, target_node = 0, max_value = 0;
/* find first node with max normal pages hit */
for (nid = 0; nid < MAX_NUMNODES; nid++)
if (khugepaged_node_load[nid] > max_value) {
max_value = khugepaged_node_load[nid];
target_node = nid;
}
/* do some balance if several nodes have the same hit record */
if (target_node <= last_khugepaged_target_node)
for (nid = last_khugepaged_target_node + 1; nid < MAX_NUMNODES;
nid++)
if (max_value == khugepaged_node_load[nid]) {
target_node = nid;
break;
}
last_khugepaged_target_node = target_node;
return target_node;
}
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
if (IS_ERR(*hpage)) {
if (!*wait)
return false;
*wait = false;
*hpage = NULL;
khugepaged_alloc_sleep();
} else if (*hpage) {
put_page(*hpage);
*hpage = NULL;
}
return true;
}
static struct page *
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
{
VM_BUG_ON_PAGE(*hpage, *hpage);
*hpage = __alloc_pages_node(node, gfp, HPAGE_PMD_ORDER);
if (unlikely(!*hpage)) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
*hpage = ERR_PTR(-ENOMEM);
return NULL;
}
prep_transhuge_page(*hpage);
count_vm_event(THP_COLLAPSE_ALLOC);
return *hpage;
}
#else
static int khugepaged_find_target_node(void)
{
return 0;
}
static inline struct page *alloc_khugepaged_hugepage(void)
{
struct page *page;
page = alloc_pages(alloc_hugepage_khugepaged_gfpmask(),
HPAGE_PMD_ORDER);
if (page)
prep_transhuge_page(page);
return page;
}
static struct page *khugepaged_alloc_hugepage(bool *wait)
{
struct page *hpage;
do {
hpage = alloc_khugepaged_hugepage();
if (!hpage) {
count_vm_event(THP_COLLAPSE_ALLOC_FAILED);
if (!*wait)
return NULL;
*wait = false;
khugepaged_alloc_sleep();
} else
count_vm_event(THP_COLLAPSE_ALLOC);
} while (unlikely(!hpage) && likely(khugepaged_enabled()));
return hpage;
}
static bool khugepaged_prealloc_page(struct page **hpage, bool *wait)
{
if (!*hpage)
*hpage = khugepaged_alloc_hugepage(wait);
if (unlikely(!*hpage))
return false;
return true;
}
static struct page *
khugepaged_alloc_page(struct page **hpage, gfp_t gfp, int node)
{
VM_BUG_ON(!*hpage);
return *hpage;
}
#endif
static bool hugepage_vma_check(struct vm_area_struct *vma)
{
if ((!(vma->vm_flags & VM_HUGEPAGE) && !khugepaged_always()) ||
(vma->vm_flags & VM_NOHUGEPAGE) ||
test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
return false;
if (shmem_file(vma->vm_file)) {
if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGE_PAGECACHE))
return false;
return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff,
HPAGE_PMD_NR);
}
if (!vma->anon_vma || vma->vm_ops)
return false;
if (is_vma_temporary_stack(vma))
return false;
return !(vma->vm_flags & VM_NO_KHUGEPAGED);
}
/*
* If mmap_sem temporarily dropped, revalidate vma
* before taking mmap_sem.
* Return 0 if succeeds, otherwise return none-zero
* value (scan code).
*/
static int hugepage_vma_revalidate(struct mm_struct *mm, unsigned long address,
struct vm_area_struct **vmap)
{
struct vm_area_struct *vma;
unsigned long hstart, hend;
if (unlikely(khugepaged_test_exit(mm)))
return SCAN_ANY_PROCESS;
*vmap = vma = find_vma(mm, address);
if (!vma)
return SCAN_VMA_NULL;
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (address < hstart || address + HPAGE_PMD_SIZE > hend)
return SCAN_ADDRESS_RANGE;
if (!hugepage_vma_check(vma))
return SCAN_VMA_CHECK;
return 0;
}
/*
* Bring missing pages in from swap, to complete THP collapse.
* Only done if khugepaged_scan_pmd believes it is worthwhile.
*
* Called and returns without pte mapped or spinlocks held,
* but with mmap_sem held to protect against vma changes.
*/
static bool __collapse_huge_page_swapin(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
int referenced)
{
int swapped_in = 0, ret = 0;
struct vm_fault vmf = {
.vma = vma,
.address = address,
.flags = FAULT_FLAG_ALLOW_RETRY,
.pmd = pmd,
.pgoff = linear_page_index(vma, address),
};
/* we only decide to swapin, if there is enough young ptes */
if (referenced < HPAGE_PMD_NR/2) {
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
return false;
}
vmf.pte = pte_offset_map(pmd, address);
for (; vmf.address < address + HPAGE_PMD_NR*PAGE_SIZE;
vmf.pte++, vmf.address += PAGE_SIZE) {
vmf.orig_pte = *vmf.pte;
if (!is_swap_pte(vmf.orig_pte))
continue;
swapped_in++;
ret = do_swap_page(&vmf);
/* do_swap_page returns VM_FAULT_RETRY with released mmap_sem */
if (ret & VM_FAULT_RETRY) {
down_read(&mm->mmap_sem);
if (hugepage_vma_revalidate(mm, address, &vmf.vma)) {
/* vma is no longer available, don't continue to swapin */
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
return false;
}
/* check if the pmd is still valid */
if (mm_find_pmd(mm, address) != pmd) {
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
return false;
}
}
if (ret & VM_FAULT_ERROR) {
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 0);
return false;
}
/* pte is unmapped now, we need to map it */
vmf.pte = pte_offset_map(pmd, vmf.address);
}
vmf.pte--;
pte_unmap(vmf.pte);
trace_mm_collapse_huge_page_swapin(mm, swapped_in, referenced, 1);
return true;
}
static void collapse_huge_page(struct mm_struct *mm,
unsigned long address,
struct page **hpage,
int node, int referenced)
{
pmd_t *pmd, _pmd;
pte_t *pte;
pgtable_t pgtable;
struct page *new_page;
spinlock_t *pmd_ptl, *pte_ptl;
int isolated = 0, result = 0;
struct mem_cgroup *memcg;
struct vm_area_struct *vma;
unsigned long mmun_start; /* For mmu_notifiers */
unsigned long mmun_end; /* For mmu_notifiers */
gfp_t gfp;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
/* Only allocate from the target node */
gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
/*
* Before allocating the hugepage, release the mmap_sem read lock.
* The allocation can take potentially a long time if it involves
* sync compaction, and we do not need to hold the mmap_sem during
* that. We will recheck the vma after taking it again in write mode.
*/
up_read(&mm->mmap_sem);
new_page = khugepaged_alloc_page(hpage, gfp, node);
if (!new_page) {
result = SCAN_ALLOC_HUGE_PAGE_FAIL;
goto out_nolock;
}
if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
result = SCAN_CGROUP_CHARGE_FAIL;
goto out_nolock;
}
down_read(&mm->mmap_sem);
result = hugepage_vma_revalidate(mm, address, &vma);
if (result) {
mem_cgroup_cancel_charge(new_page, memcg, true);
up_read(&mm->mmap_sem);
goto out_nolock;
}
pmd = mm_find_pmd(mm, address);
if (!pmd) {
result = SCAN_PMD_NULL;
mem_cgroup_cancel_charge(new_page, memcg, true);
up_read(&mm->mmap_sem);
goto out_nolock;
}
/*
* __collapse_huge_page_swapin always returns with mmap_sem locked.
* If it fails, we release mmap_sem and jump out_nolock.
* Continuing to collapse causes inconsistency.
*/
if (!__collapse_huge_page_swapin(mm, vma, address, pmd, referenced)) {
mem_cgroup_cancel_charge(new_page, memcg, true);
up_read(&mm->mmap_sem);
goto out_nolock;
}
up_read(&mm->mmap_sem);
/*
* Prevent all access to pagetables with the exception of
* gup_fast later handled by the ptep_clear_flush and the VM
* handled by the anon_vma lock + PG_lock.
*
* UFFDIO_REMAP is prevented to race as well thanks to the
* mmap_sem.
*/
down_write(&mm->mmap_sem);
result = hugepage_vma_revalidate(mm, address, &vma);
if (result)
goto out;
/* check if the pmd is still valid */
if (mm_find_pmd(mm, address) != pmd)
goto out;
anon_vma_lock_write(vma->anon_vma);
pte = pte_offset_map(pmd, address);
pte_ptl = pte_lockptr(mm, pmd);
mmun_start = address;
mmun_end = address + HPAGE_PMD_SIZE;
mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end);
pmd_ptl = pmd_lock(mm, pmd); /* probably unnecessary */
/*
* After this gup_fast can't run anymore. This also removes
* any huge TLB entry from the CPU so we won't allow
* huge and small TLB entries for the same virtual address
* to avoid the risk of CPU bugs in that area.
*/
_pmd = pmdp_collapse_flush(vma, address, pmd);
spin_unlock(pmd_ptl);
mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
spin_lock(pte_ptl);
isolated = __collapse_huge_page_isolate(vma, address, pte);
spin_unlock(pte_ptl);
if (unlikely(!isolated)) {
pte_unmap(pte);
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
/*
* We can only use set_pmd_at when establishing
* hugepmds and never for establishing regular pmds that
* points to regular pagetables. Use pmd_populate for that
*/
pmd_populate(mm, pmd, pmd_pgtable(_pmd));
spin_unlock(pmd_ptl);
anon_vma_unlock_write(vma->anon_vma);
result = SCAN_FAIL;
goto out;
}
/*
* All pages are isolated and locked so anon_vma rmap
* can't run anymore.
*/
anon_vma_unlock_write(vma->anon_vma);
__collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl);
pte_unmap(pte);
__SetPageUptodate(new_page);
pgtable = pmd_pgtable(_pmd);
_pmd = mk_huge_pmd(new_page, vma->vm_page_prot);
_pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma);
/*
* spin_lock() below is not the equivalent of smp_wmb(), so
* this is needed to avoid the copy_huge_page writes to become
* visible after the set_pmd_at() write.
*/
smp_wmb();
spin_lock(pmd_ptl);
BUG_ON(!pmd_none(*pmd));
page_add_new_anon_rmap(new_page, vma, address, true);
mem_cgroup_commit_charge(new_page, memcg, false, true);
lru_cache_add_active_or_unevictable(new_page, vma);
pgtable_trans_huge_deposit(mm, pmd, pgtable);
set_pmd_at(mm, address, pmd, _pmd);
update_mmu_cache_pmd(vma, address, pmd);
spin_unlock(pmd_ptl);
*hpage = NULL;
khugepaged_pages_collapsed++;
result = SCAN_SUCCEED;
out_up_write:
up_write(&mm->mmap_sem);
out_nolock:
trace_mm_collapse_huge_page(mm, isolated, result);
return;
out:
mem_cgroup_cancel_charge(new_page, memcg, true);
goto out_up_write;
}
static int khugepaged_scan_pmd(struct mm_struct *mm,
struct vm_area_struct *vma,
unsigned long address,
struct page **hpage)
{
pmd_t *pmd;
pte_t *pte, *_pte;
int ret = 0, none_or_zero = 0, result = 0, referenced = 0;
struct page *page = NULL;
unsigned long _address;
spinlock_t *ptl;
int node = NUMA_NO_NODE, unmapped = 0;
bool writable = false;
VM_BUG_ON(address & ~HPAGE_PMD_MASK);
pmd = mm_find_pmd(mm, address);
if (!pmd) {
result = SCAN_PMD_NULL;
goto out;
}
memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
pte = pte_offset_map_lock(mm, pmd, address, &ptl);
for (_address = address, _pte = pte; _pte < pte+HPAGE_PMD_NR;
_pte++, _address += PAGE_SIZE) {
pte_t pteval = *_pte;
if (is_swap_pte(pteval)) {
if (++unmapped <= khugepaged_max_ptes_swap) {
continue;
} else {
result = SCAN_EXCEED_SWAP_PTE;
goto out_unmap;
}
}
if (pte_none(pteval) || is_zero_pfn(pte_pfn(pteval))) {
if (!userfaultfd_armed(vma) &&
++none_or_zero <= khugepaged_max_ptes_none) {
continue;
} else {
result = SCAN_EXCEED_NONE_PTE;
goto out_unmap;
}
}
if (!pte_present(pteval)) {
result = SCAN_PTE_NON_PRESENT;
goto out_unmap;
}
if (pte_write(pteval))
writable = true;
page = vm_normal_page(vma, _address, pteval);
if (unlikely(!page)) {
result = SCAN_PAGE_NULL;
goto out_unmap;
}
/* TODO: teach khugepaged to collapse THP mapped with pte */
if (PageCompound(page)) {
result = SCAN_PAGE_COMPOUND;
goto out_unmap;
}
/*
* Record which node the original page is from and save this
* information to khugepaged_node_load[].
* Khupaged will allocate hugepage from the node has the max
* hit record.
*/
node = page_to_nid(page);
if (khugepaged_scan_abort(node)) {
result = SCAN_SCAN_ABORT;
goto out_unmap;
}
khugepaged_node_load[node]++;
if (!PageLRU(page)) {
result = SCAN_PAGE_LRU;
goto out_unmap;
}
if (PageLocked(page)) {
result = SCAN_PAGE_LOCK;
goto out_unmap;
}
if (!PageAnon(page)) {
result = SCAN_PAGE_ANON;
goto out_unmap;
}
/*
* cannot use mapcount: can't collapse if there's a gup pin.
* The page must only be referenced by the scanned process
* and page swap cache.
*/
if (page_count(page) != 1 + PageSwapCache(page)) {
result = SCAN_PAGE_COUNT;
goto out_unmap;
}
if (pte_young(pteval) ||
page_is_young(page) || PageReferenced(page) ||
mmu_notifier_test_young(vma->vm_mm, address))
referenced++;
}
if (writable) {
if (referenced) {
result = SCAN_SUCCEED;
ret = 1;
} else {
result = SCAN_LACK_REFERENCED_PAGE;
}
} else {
result = SCAN_PAGE_RO;
}
out_unmap:
pte_unmap_unlock(pte, ptl);
if (ret) {
node = khugepaged_find_target_node();
/* collapse_huge_page will return with the mmap_sem released */
collapse_huge_page(mm, address, hpage, node, referenced);
}
out:
trace_mm_khugepaged_scan_pmd(mm, page, writable, referenced,
none_or_zero, result, unmapped);
return ret;
}
static void collect_mm_slot(struct mm_slot *mm_slot)
{
struct mm_struct *mm = mm_slot->mm;
VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
if (khugepaged_test_exit(mm)) {
/* free mm_slot */
hash_del(&mm_slot->hash);
list_del(&mm_slot->mm_node);
/*
* Not strictly needed because the mm exited already.
*
* clear_bit(MMF_VM_HUGEPAGE, &mm->flags);
*/
/* khugepaged_mm_lock actually not necessary for the below */
free_mm_slot(mm_slot);
mmdrop(mm);
}
}
#if defined(CONFIG_SHMEM) && defined(CONFIG_TRANSPARENT_HUGE_PAGECACHE)
static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
{
struct vm_area_struct *vma;
unsigned long addr;
pmd_t *pmd, _pmd;
i_mmap_lock_write(mapping);
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
/* probably overkill */
if (vma->anon_vma)
continue;
addr = vma->vm_start + ((pgoff - vma->vm_pgoff) << PAGE_SHIFT);
if (addr & ~HPAGE_PMD_MASK)
continue;
if (vma->vm_end < addr + HPAGE_PMD_SIZE)
continue;
pmd = mm_find_pmd(vma->vm_mm, addr);
if (!pmd)
continue;
/*
* We need exclusive mmap_sem to retract page table.
* If trylock fails we would end up with pte-mapped THP after
* re-fault. Not ideal, but it's more important to not disturb
* the system too much.
*/
if (down_write_trylock(&vma->vm_mm->mmap_sem)) {
spinlock_t *ptl = pmd_lock(vma->vm_mm, pmd);
/* assume page table is clear */
_pmd = pmdp_collapse_flush(vma, addr, pmd);
spin_unlock(ptl);
up_write(&vma->vm_mm->mmap_sem);
mm_dec_nr_ptes(vma->vm_mm);
pte_free(vma->vm_mm, pmd_pgtable(_pmd));
}
}
i_mmap_unlock_write(mapping);
}
/**
* collapse_shmem - collapse small tmpfs/shmem pages into huge one.
*
* Basic scheme is simple, details are more complex:
* - allocate and freeze a new huge page;
* - scan over radix tree replacing old pages the new one
* + swap in pages if necessary;
* + fill in gaps;
* + keep old pages around in case if rollback is required;
* - if replacing succeed:
* + copy data over;
* + free old pages;
* + unfreeze huge page;
* - if replacing failed;
* + put all pages back and unfreeze them;
* + restore gaps in the radix-tree;
* + free huge page;
*/
static void collapse_shmem(struct mm_struct *mm,
struct address_space *mapping, pgoff_t start,
struct page **hpage, int node)
{
gfp_t gfp;
struct page *page, *new_page, *tmp;
struct mem_cgroup *memcg;
pgoff_t index, end = start + HPAGE_PMD_NR;
LIST_HEAD(pagelist);
struct radix_tree_iter iter;
void **slot;
int nr_none = 0, result = SCAN_SUCCEED;
VM_BUG_ON(start & (HPAGE_PMD_NR - 1));
/* Only allocate from the target node */
gfp = alloc_hugepage_khugepaged_gfpmask() | __GFP_THISNODE;
new_page = khugepaged_alloc_page(hpage, gfp, node);
if (!new_page) {
result = SCAN_ALLOC_HUGE_PAGE_FAIL;
goto out;
}
if (unlikely(mem_cgroup_try_charge(new_page, mm, gfp, &memcg, true))) {
result = SCAN_CGROUP_CHARGE_FAIL;
goto out;
}
new_page->index = start;
new_page->mapping = mapping;
__SetPageSwapBacked(new_page);
__SetPageLocked(new_page);
BUG_ON(!page_ref_freeze(new_page, 1));
/*
* At this point the new_page is 'frozen' (page_count() is zero), locked
* and not up-to-date. It's safe to insert it into radix tree, because
* nobody would be able to map it or use it in other way until we
* unfreeze it.
*/
index = start;
spin_lock_irq(&mapping->tree_lock);
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
int n = min(iter.index, end) - index;
/*
* Handle holes in the radix tree: charge it from shmem and
* insert relevant subpage of new_page into the radix-tree.
*/
if (n && !shmem_charge(mapping->host, n)) {
result = SCAN_FAIL;
break;
}
nr_none += n;
for (; index < min(iter.index, end); index++) {
radix_tree_insert(&mapping->page_tree, index,
new_page + (index % HPAGE_PMD_NR));
}
/* We are done. */
if (index >= end)
break;
page = radix_tree_deref_slot_protected(slot,
&mapping->tree_lock);
if (radix_tree_exceptional_entry(page) || !PageUptodate(page)) {
spin_unlock_irq(&mapping->tree_lock);
/* swap in or instantiate fallocated page */
if (shmem_getpage(mapping->host, index, &page,
SGP_NOHUGE)) {
result = SCAN_FAIL;
goto tree_unlocked;
}
spin_lock_irq(&mapping->tree_lock);
} else if (trylock_page(page)) {
get_page(page);
} else {
result = SCAN_PAGE_LOCK;
break;
}
/*
* The page must be locked, so we can drop the tree_lock
* without racing with truncate.
*/
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(!PageUptodate(page), page);
VM_BUG_ON_PAGE(PageTransCompound(page), page);
if (page_mapping(page) != mapping) {
result = SCAN_TRUNCATED;
goto out_unlock;
}
spin_unlock_irq(&mapping->tree_lock);
if (isolate_lru_page(page)) {
result = SCAN_DEL_PAGE_LRU;
goto out_isolate_failed;
}
if (page_mapped(page))
unmap_mapping_pages(mapping, index, 1, false);
spin_lock_irq(&mapping->tree_lock);
slot = radix_tree_lookup_slot(&mapping->page_tree, index);
VM_BUG_ON_PAGE(page != radix_tree_deref_slot_protected(slot,
&mapping->tree_lock), page);
VM_BUG_ON_PAGE(page_mapped(page), page);
/*
* The page is expected to have page_count() == 3:
* - we hold a pin on it;
* - one reference from radix tree;
* - one from isolate_lru_page;
*/
if (!page_ref_freeze(page, 3)) {
result = SCAN_PAGE_COUNT;
goto out_lru;
}
/*
* Add the page to the list to be able to undo the collapse if
* something go wrong.
*/
list_add_tail(&page->lru, &pagelist);
/* Finally, replace with the new page. */
radix_tree_replace_slot(&mapping->page_tree, slot,
new_page + (index % HPAGE_PMD_NR));
slot = radix_tree_iter_resume(slot, &iter);
index++;
continue;
out_lru:
spin_unlock_irq(&mapping->tree_lock);
putback_lru_page(page);
out_isolate_failed:
unlock_page(page);
put_page(page);
goto tree_unlocked;
out_unlock:
unlock_page(page);
put_page(page);
break;
}
/*
* Handle hole in radix tree at the end of the range.
* This code only triggers if there's nothing in radix tree
* beyond 'end'.
*/
if (result == SCAN_SUCCEED && index < end) {
int n = end - index;
if (!shmem_charge(mapping->host, n)) {
result = SCAN_FAIL;
goto tree_locked;
}
for (; index < end; index++) {
radix_tree_insert(&mapping->page_tree, index,
new_page + (index % HPAGE_PMD_NR));
}
nr_none += n;
}
tree_locked:
spin_unlock_irq(&mapping->tree_lock);
tree_unlocked:
if (result == SCAN_SUCCEED) {
unsigned long flags;
struct zone *zone = page_zone(new_page);
/*
* Replacing old pages with new one has succeed, now we need to
* copy the content and free old pages.
*/
list_for_each_entry_safe(page, tmp, &pagelist, lru) {
copy_highpage(new_page + (page->index % HPAGE_PMD_NR),
page);
list_del(&page->lru);
unlock_page(page);
page_ref_unfreeze(page, 1);
page->mapping = NULL;
ClearPageActive(page);
ClearPageUnevictable(page);
put_page(page);
}
local_irq_save(flags);
__inc_node_page_state(new_page, NR_SHMEM_THPS);
if (nr_none) {
__mod_node_page_state(zone->zone_pgdat, NR_FILE_PAGES, nr_none);
__mod_node_page_state(zone->zone_pgdat, NR_SHMEM, nr_none);
}
local_irq_restore(flags);
/*
* Remove pte page tables, so we can re-faulti
* the page as huge.
*/
retract_page_tables(mapping, start);
/* Everything is ready, let's unfreeze the new_page */
set_page_dirty(new_page);
SetPageUptodate(new_page);
page_ref_unfreeze(new_page, HPAGE_PMD_NR);
mem_cgroup_commit_charge(new_page, memcg, false, true);
lru_cache_add_anon(new_page);
unlock_page(new_page);
*hpage = NULL;
} else {
/* Something went wrong: rollback changes to the radix-tree */
shmem_uncharge(mapping->host, nr_none);
spin_lock_irq(&mapping->tree_lock);
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
start) {
if (iter.index >= end)
break;
page = list_first_entry_or_null(&pagelist,
struct page, lru);
if (!page || iter.index < page->index) {
if (!nr_none)
break;
nr_none--;
/* Put holes back where they were */
radix_tree_delete(&mapping->page_tree,
iter.index);
continue;
}
VM_BUG_ON_PAGE(page->index != iter.index, page);
/* Unfreeze the page. */
list_del(&page->lru);
page_ref_unfreeze(page, 2);
radix_tree_replace_slot(&mapping->page_tree,
slot, page);
slot = radix_tree_iter_resume(slot, &iter);
spin_unlock_irq(&mapping->tree_lock);
putback_lru_page(page);
unlock_page(page);
spin_lock_irq(&mapping->tree_lock);
}
VM_BUG_ON(nr_none);
spin_unlock_irq(&mapping->tree_lock);
/* Unfreeze new_page, caller would take care about freeing it */
page_ref_unfreeze(new_page, 1);
mem_cgroup_cancel_charge(new_page, memcg, true);
unlock_page(new_page);
new_page->mapping = NULL;
}
out:
VM_BUG_ON(!list_empty(&pagelist));
/* TODO: tracepoints */
}
static void khugepaged_scan_shmem(struct mm_struct *mm,
struct address_space *mapping,
pgoff_t start, struct page **hpage)
{
struct page *page = NULL;
struct radix_tree_iter iter;
void **slot;
int present, swap;
int node = NUMA_NO_NODE;
int result = SCAN_SUCCEED;
present = 0;
swap = 0;
memset(khugepaged_node_load, 0, sizeof(khugepaged_node_load));
rcu_read_lock();
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) {
if (iter.index >= start + HPAGE_PMD_NR)
break;
page = radix_tree_deref_slot(slot);
if (radix_tree_deref_retry(page)) {
slot = radix_tree_iter_retry(&iter);
continue;
}
if (radix_tree_exception(page)) {
if (++swap > khugepaged_max_ptes_swap) {
result = SCAN_EXCEED_SWAP_PTE;
break;
}
continue;
}
if (PageTransCompound(page)) {
result = SCAN_PAGE_COMPOUND;
break;
}
node = page_to_nid(page);
if (khugepaged_scan_abort(node)) {
result = SCAN_SCAN_ABORT;
break;
}
khugepaged_node_load[node]++;
if (!PageLRU(page)) {
result = SCAN_PAGE_LRU;
break;
}
if (page_count(page) != 1 + page_mapcount(page)) {
result = SCAN_PAGE_COUNT;
break;
}
/*
* We probably should check if the page is referenced here, but
* nobody would transfer pte_young() to PageReferenced() for us.
* And rmap walk here is just too costly...
*/
present++;
if (need_resched()) {
slot = radix_tree_iter_resume(slot, &iter);
cond_resched_rcu();
}
}
rcu_read_unlock();
if (result == SCAN_SUCCEED) {
if (present < HPAGE_PMD_NR - khugepaged_max_ptes_none) {
result = SCAN_EXCEED_NONE_PTE;
} else {
node = khugepaged_find_target_node();
collapse_shmem(mm, mapping, start, hpage, node);
}
}
/* TODO: tracepoints */
}
#else
static void khugepaged_scan_shmem(struct mm_struct *mm,
struct address_space *mapping,
pgoff_t start, struct page **hpage)
{
BUILD_BUG();
}
#endif
static unsigned int khugepaged_scan_mm_slot(unsigned int pages,
struct page **hpage)
__releases(&khugepaged_mm_lock)
__acquires(&khugepaged_mm_lock)
{
struct mm_slot *mm_slot;
struct mm_struct *mm;
struct vm_area_struct *vma;
int progress = 0;
VM_BUG_ON(!pages);
VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&khugepaged_mm_lock));
if (khugepaged_scan.mm_slot)
mm_slot = khugepaged_scan.mm_slot;
else {
mm_slot = list_entry(khugepaged_scan.mm_head.next,
struct mm_slot, mm_node);
khugepaged_scan.address = 0;
khugepaged_scan.mm_slot = mm_slot;
}
spin_unlock(&khugepaged_mm_lock);
mm = mm_slot->mm;
/*
* Don't wait for semaphore (to avoid long wait times). Just move to
* the next mm on the list.
*/
vma = NULL;
if (unlikely(!down_read_trylock(&mm->mmap_sem)))
goto breakouterloop_mmap_sem;
if (likely(!khugepaged_test_exit(mm)))
vma = find_vma(mm, khugepaged_scan.address);
progress++;
for (; vma; vma = vma->vm_next) {
unsigned long hstart, hend;
cond_resched();
if (unlikely(khugepaged_test_exit(mm))) {
progress++;
break;
}
if (!hugepage_vma_check(vma)) {
skip:
progress++;
continue;
}
hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
hend = vma->vm_end & HPAGE_PMD_MASK;
if (hstart >= hend)
goto skip;
if (khugepaged_scan.address > hend)
goto skip;
if (khugepaged_scan.address < hstart)
khugepaged_scan.address = hstart;
VM_BUG_ON(khugepaged_scan.address & ~HPAGE_PMD_MASK);
while (khugepaged_scan.address < hend) {
int ret;
cond_resched();
if (unlikely(khugepaged_test_exit(mm)))
goto breakouterloop;
VM_BUG_ON(khugepaged_scan.address < hstart ||
khugepaged_scan.address + HPAGE_PMD_SIZE >
hend);
if (shmem_file(vma->vm_file)) {
struct file *file;
pgoff_t pgoff = linear_page_index(vma,
khugepaged_scan.address);
if (!shmem_huge_enabled(vma))
goto skip;
file = get_file(vma->vm_file);
up_read(&mm->mmap_sem);
ret = 1;
khugepaged_scan_shmem(mm, file->f_mapping,
pgoff, hpage);
fput(file);
} else {
ret = khugepaged_scan_pmd(mm, vma,
khugepaged_scan.address,
hpage);
}
/* move to next address */
khugepaged_scan.address += HPAGE_PMD_SIZE;
progress += HPAGE_PMD_NR;
if (ret)
/* we released mmap_sem so break loop */
goto breakouterloop_mmap_sem;
if (progress >= pages)
goto breakouterloop;
}
}
breakouterloop:
up_read(&mm->mmap_sem); /* exit_mmap will destroy ptes after this */
breakouterloop_mmap_sem:
spin_lock(&khugepaged_mm_lock);
VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
/*
* Release the current mm_slot if this mm is about to die, or
* if we scanned all vmas of this mm.
*/
if (khugepaged_test_exit(mm) || !vma) {
/*
* Make sure that if mm_users is reaching zero while
* khugepaged runs here, khugepaged_exit will find
* mm_slot not pointing to the exiting mm.
*/
if (mm_slot->mm_node.next != &khugepaged_scan.mm_head) {
khugepaged_scan.mm_slot = list_entry(
mm_slot->mm_node.next,
struct mm_slot, mm_node);
khugepaged_scan.address = 0;
} else {
khugepaged_scan.mm_slot = NULL;
khugepaged_full_scans++;
}
collect_mm_slot(mm_slot);
}
return progress;
}
static int khugepaged_has_work(void)
{
return !list_empty(&khugepaged_scan.mm_head) &&
khugepaged_enabled();
}
static int khugepaged_wait_event(void)
{
return !list_empty(&khugepaged_scan.mm_head) ||
kthread_should_stop();
}
static void khugepaged_do_scan(void)
{
struct page *hpage = NULL;
unsigned int progress = 0, pass_through_head = 0;
unsigned int pages = khugepaged_pages_to_scan;
bool wait = true;
barrier(); /* write khugepaged_pages_to_scan to local stack */
while (progress < pages) {
if (!khugepaged_prealloc_page(&hpage, &wait))
break;
cond_resched();
if (unlikely(kthread_should_stop() || try_to_freeze()))
break;
spin_lock(&khugepaged_mm_lock);
if (!khugepaged_scan.mm_slot)
pass_through_head++;
if (khugepaged_has_work() &&
pass_through_head < 2)
progress += khugepaged_scan_mm_slot(pages - progress,
&hpage);
else
progress = pages;
spin_unlock(&khugepaged_mm_lock);
}
if (!IS_ERR_OR_NULL(hpage))
put_page(hpage);
}
static bool khugepaged_should_wakeup(void)
{
return kthread_should_stop() ||
time_after_eq(jiffies, khugepaged_sleep_expire);
}
static void khugepaged_wait_work(void)
{
if (khugepaged_has_work()) {
const unsigned long scan_sleep_jiffies =
msecs_to_jiffies(khugepaged_scan_sleep_millisecs);
if (!scan_sleep_jiffies)
return;
khugepaged_sleep_expire = jiffies + scan_sleep_jiffies;
wait_event_freezable_timeout(khugepaged_wait,
khugepaged_should_wakeup(),
scan_sleep_jiffies);
return;
}
if (khugepaged_enabled())
wait_event_freezable(khugepaged_wait, khugepaged_wait_event());
}
static int khugepaged(void *none)
{
struct mm_slot *mm_slot;
set_freezable();
set_user_nice(current, MAX_NICE);
while (!kthread_should_stop()) {
khugepaged_do_scan();
khugepaged_wait_work();
}
spin_lock(&khugepaged_mm_lock);
mm_slot = khugepaged_scan.mm_slot;
khugepaged_scan.mm_slot = NULL;
if (mm_slot)
collect_mm_slot(mm_slot);
spin_unlock(&khugepaged_mm_lock);
return 0;
}
static void set_recommended_min_free_kbytes(void)
{
struct zone *zone;
int nr_zones = 0;
unsigned long recommended_min;
for_each_populated_zone(zone)
nr_zones++;
/* Ensure 2 pageblocks are free to assist fragmentation avoidance */
recommended_min = pageblock_nr_pages * nr_zones * 2;
/*
* Make sure that on average at least two pageblocks are almost free
* of another type, one for a migratetype to fall back to and a
* second to avoid subsequent fallbacks of other types There are 3
* MIGRATE_TYPES we care about.
*/
recommended_min += pageblock_nr_pages * nr_zones *
MIGRATE_PCPTYPES * MIGRATE_PCPTYPES;
/* don't ever allow to reserve more than 5% of the lowmem */
recommended_min = min(recommended_min,
(unsigned long) nr_free_buffer_pages() / 20);
recommended_min <<= (PAGE_SHIFT-10);
if (recommended_min > min_free_kbytes) {
if (user_min_free_kbytes >= 0)
pr_info("raising min_free_kbytes from %d to %lu to help transparent hugepage allocations\n",
min_free_kbytes, recommended_min);
min_free_kbytes = recommended_min;
}
setup_per_zone_wmarks();
}
int start_stop_khugepaged(void)
{
static struct task_struct *khugepaged_thread __read_mostly;
static DEFINE_MUTEX(khugepaged_mutex);
int err = 0;
mutex_lock(&khugepaged_mutex);
if (khugepaged_enabled()) {
if (!khugepaged_thread)
khugepaged_thread = kthread_run(khugepaged, NULL,
"khugepaged");
if (IS_ERR(khugepaged_thread)) {
pr_err("khugepaged: kthread_run(khugepaged) failed\n");
err = PTR_ERR(khugepaged_thread);
khugepaged_thread = NULL;
goto fail;
}
if (!list_empty(&khugepaged_scan.mm_head))
wake_up_interruptible(&khugepaged_wait);
set_recommended_min_free_kbytes();
} else if (khugepaged_thread) {
kthread_stop(khugepaged_thread);
khugepaged_thread = NULL;
}
fail:
mutex_unlock(&khugepaged_mutex);
return err;
}